Speaking to The News, Ms Mordaunt said: ‘He would be bad for Portsmouth, and bad for the country.

‘I really don’t think he can appreciate the threats we are facing – not just threats he would associate with the Cold War.

‘We have a resurgent Russia, an increasingly aggressive Russia, we have these old, familiar concerns.

‘But we also have a massive, fast-moving rise in cyber warfare.

‘We need to work ever more closely with our countries and allies.

‘To not realise that, he can’t have a grip on what is going on in the world today.

‘It is the first priority of any government to protect the UK.’

Mr Corbyn, who is in the Labour race against Andy Burnham, Liz Kendall and Yvette Cooper, was given a warm reception this week as he visited teh Hilton Hotel at the Ageas Bowl to address Labour supporters and speak out against austerity measures.